The invention relates to a fuel injection valve for internal combustion engines.
Published European Patent Application No. EP 0 352 926 discloses a fuel injection valve having a piston-shaped valve member, which is axially displaceable in a valve body, and having a tapered valve sealing face at its end on the combustion chamber side. With the tapered valve sealing face the valve member interacts with a tapered valve seat face provided at a closed end of a bore in the valve body, a sealing cross section being formed at the line of contact between the valve sealing face and the valve seat face. Injection holes are provided downstream of the sealing cross section as seen in the fuel flow direction. These injection holes are provided in the wall of the valve body and extend from the bore in the valve body to the external cylindrical surface of the valve body and in so doing project into the combustion chamber of the internal combustion engine to be supplied with fuel. The injection holes of the fuel injection valve have a tapered form, the cross section of the injection holes tapering uniformly and conically from a relatively large diameter at the fuel inlet to a relatively small diameter at the fuel outlet.
A disadvantage of this conventional fuel injection valve is however that all injection holes have the same degree of taper of their conical shape, so that it is not possible to adjust the individual fuel injection jet at each injection hole separately to suit the respective requirements of the individual injection jet inside the combustion chamber. This individual optimization of the individual jet geometries at each injection hole is however of considerable importance, especially in the case of an eccentric or slanted installation position of the fuel injection valve in the combustion chamber of the internal combustion engine, since only by this individual optimization is it possible to optimize the fuel injection, in terms of the jet geometry and the jet preparation, to suit the respective conditions in the combustion chamber of the internal combustion engine, and thus to achieve optimum fuel preparation and combustion. Such optimization of the jet geometry at each jet entry into the combustion chamber is, however, not possible using the above-described fuel injection valve.
It is accordingly an object of the invention to provide a fuel injection valve which overcomes the above-mentioned disadvantages of the heretofore-known fuel injection valves of this general type and which allows an optimized injection of fuel.
With the foregoing and other objects in view there is provided, in accordance with the invention, a fuel injection valve for an internal combustion engine, including:
a valve body having a valve seat face provided thereon, the valve body defining an axial direction;
a valve member having an end region on a combustion chamber-side thereof and having a valve sealing.face in the end region, the valve sealing face interacting with the valve seat face of the valve body for forming a sealing cross section;
the valve member being displaceable along the axial direction in the valve body;
the valve body having a wall with injection holes formed therein, the injection holes being provided downstream from the sealing cross section as seen in a fuel flow direction; and
the injection holes being cone-shaped injection holes, at least two of the injection holes having respectively different cone angles.
The fuel injection valve according to the invention, that is intended for internal combustion engines, has the advantage that at each injection hole it is possible to optimize the injection jet geometry or injection spray geometry as a function of the local requirements. For this purpose the injection holes have different angles of taper from one another, i.e. different angles of taper for the cone-shaped injection holes, by way of which the respective fuel flow and hence the injected fuel jet can be individually formed or shaped. In order to achieve this, it is possible to reduce the cross section of the injection hole uniformly from a large diameter to a small diameter in the direction of flow of the fuel. This is called a positive degree of taper or positive conical shape.
Alternatively, it is also possible, however, given corresponding requirements, to increase the cross section of the injection hole (spray hole) uniformly from the inlet aperture toward the outlet aperture on the combustion chamber side. This is called negative degree of (conical) taper.
According to an advantageous feature of the invention, at least two injection holes, depending upon the installation position of the fuel injection valve in the combustion chamber of the internal combustion engine to be supplied with fuel, have different angles of conical taper from one another. The angles of conical taper are preferably in a range between 10xc2x0 and 90xc2x0.
According to another feature of the invention, it is particularly advantageous to increase the deflection angle (which is preferably between 15xc2x0 and as much as 120xc2x0 in exceptional installation cases) of the inlet fuel at the inlet into the injection hole, if the angle of taper is also increased, especially in the case of a positive conical taper.
According to another feature of the invention, a number of the injection holes are provided one over another along the axial direction.
According to yet another feature of the invention, the injection holes together with the wall of the valve body define respective deflection angles by which deflection angles the fuel flowing into the injection holes is deflected when entering the injection holes, and the cone angles are a function of the deflection angles such that given ones of the injection holes, which have substantially identical deflection angles, have substantially identical cone angles.
A plurality of injection holes may be provided on the fuel injection valve, wherein it is possible to provide the injection holes of varying configuration in a row around the circumference of the injection valve.
Alternatively, it is also possible, however, to provide a plurality of rows of injection holes, the rows being provided one over another, as seen in an axial direction, on the fuel injection valve, which can moreover be successively opened through corresponding actuation of the axially moveable valve member.
In addition, it is particularly advantageous for the fuel inlet flow into the injection hole if the inlet edges on the injection hole are radiused, i.e. the inlet edges are rounded off. This avoids swirling or turbulences at this point and thereby prevents the occurrence of regions of diminished pressure, so that the inlet fuel can flow evenly into the injection hole. This measure also assists in forming the fuel flow inside the injection hole into the desired geometry of the injected fuel jet at the outlet of the injection hole.
With the fuel injection valve according to the invention for internal combustion engines it is therefore possible to advantageously provide each individual injection hole with an individual, optimized degree of taper according to the required fuel flow and jet geometry at the outlet, whilst the angle of taper of the corresponding injection hole may be either positive or negative. An optimized, individual configuring of the angle of taper at the individual injection holes thus means that the same mean velocity of fuel flow can be produced at each spray hole outlet, despite the differing deflection angle of the inlet fuel and a slanted installation position of the fuel injection valve in the combustion chamber.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fuel injection valve for internal combustion engines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.